The present invention relates to a multiple electric motor driven centrifugal air compressor, for example, for gasoline or diesel engine powered vehicles.
There is a problem with previous centrifugal air compressor designs when used as an engine""s supercharger, in that a single electrical motor is ineffective in providing the required power needed to produce the air flow (cfm) and minimum boost pressure (at least 5 psi) that results in a noticeable horsepower (hp) increase. A single electric motor is limited by the motor""s amperage draw (watts) and to the capacity of a vehicle""s battery(s) and electrical system (i.e. battery cables).
The present invention uses existing and well-known centrifugal air compressor (supercharger) theory and design, then combines that with two or more high power electric motors. The multiple electric motors have drive pulleys affixed to one end inside a common housing, which then drives a pulley that is on a common shaft with the centrifugal supercharger""s impeller. The centrifugal supercharger""s impeller is turned by a driven pulley which is connected by an endless belt to said pulleys that are affixed to the multiple electric motors mounted to a common housing. Previous electric superchargers have used a single electric motor connected to the centrifugal compressor on a common fixed shaft.
Any engine""s power output can be increased an additional amount by forcing air into the engine at pressures above atmospheric pressure (14.7 psi). Any given engine will experience an average one hundred percent (100%) increase in power with the addition of a second atmosphere of pressure (14.7 psi+14.7 psi) to the intake manifold. To create additional pressure (boost) and additional airflow (cfm) through an engine takes a considerable amount of power. For example, a 2.0 liter, 4 cylinder engine that turns 6000 rpm will flow 216 cfm. To flow 50% more air (324 cfm) and 50% more pressure (7.4 psi) would require 14 hp. (14 hp=10,444 watts (14 hpxc3x97746 watts/hp)). Using common electrical laws, 10,444 watts is equal to 870 amps (watts=voltsxc3x97amps). Therein lies one of the problems with the prior art. It is virtually impossible to get 870 amps at 12 volts from one electric motor. Another problem is also evident, a single electric motor sufficient to make 14 hp would be extremely heavy, very large and would make fitment an impossibility on most vehicles. The rotational speed of the compressor impeller (rotor, wheel) would also be an additional problem. A centrifugal compressor, by design, requires extremely high rotational speeds. These rotational speeds are 30,000 rpm and higher. To design a 12 volt motor capable of 14 hp at 30,000 rpm is impractical, if not impossible.
The prior art has additional shortcomings in the vehicles battery(s) and cables used to power the supercharger. Standard automotive batteries are rated using cold cranking amps (cca). Factory supplied standard automotive batteries are typically rated at 500 cca. The battery cables pose an additional limitation. The largest standard automotive battery cable is the #2 size, rated at 205 amps continuous, or 275 amps momentary. 205 ampsxc3x9712 volts=2460 watts, or 3.3 hp. The typical automotive starter is rated at 1 to 1.5 hp, so the #2 cable is adequate for that application. The present supercharger design draws 14,000 watts (18 hp), or 1166 amps at 12 volts. It is therefore impossible for a single battery and set of battery cables to provide the necessary watts to generate 18 hp.
One purpose of the present invention is to allow for electric supercharger performance previously unattainable. A single electric motor is limited by size, weight, amperage, rpm rotational speed, the battery, and battery cable system. By using multiple (two or more) electric motors combined with separate multiple batteries and battery cable/wiring, each electric motor having its own set of battery(s), relay(s) and cables, the previous power limitations are overcome. By using an overdrive pulley and belt design, the required compressor impeller rotational speeds are obtained.
The present invention obtains the desired higher than atmospheric pressure that results in a large increase in horse power (HP) on engines.
The present invention utilizes two (2) or more 3,000+ watt, high RPM (9000+ RPM) motors, each motor having a large drive pulley affixed to one end, on a common mounting plate/housing with parallel shafts turning a smaller driven pulley which turns the centrifugal supercharger impeller. The approximate overdrive ratio is between 2.5:1 and 4:1. This step-up ratio is necessary to obtain the desired 30,000+ impeller rotational speeds to create 5+ psi boost pressure on engines up to 4.0 liters. Larger engines would, of course, require two or more electric superchargers.
One embodiment of the present invention provides a compact design of three electric motors, with each motor measuring five (5) to six (6) inches long, making the complete electric supercharger eleven (11) to twelve (12) inches long, ten (10) inches in diameter, and weighing approximately 38 lbs. This is similar in size to popular centrifugal superchargers.
One embodiment of the present invention incorporates the use of three separate batteries to power the supercharger unitxe2x80x94one battery per electric motor, with one complete set of battery cables and relays per battery/electric motor. The three sets of battery cables are to be larger than production battery cables, 2/0 cables rated at 325 amps (continuous) per cable. The 2/0 cables have a momentary rating of 450 amps (30 seconds) per cable, allowing for 1350 amps or 16,200 watts (450 ampsxc3x973 batteriesxc3x9712 volts).
One embodiment of this invention uses two idler pulleys, with one acting as an adjustable tensioner with the endless belt wrapping around the three drive pulleys, the one driven pulley and both idler pulleys.
Another embodiment of the present invention uses an endless belt wrapping around three drive pulleys, thereby driving one driven pulley, and may nor may not use one or more tensioner/idler pulley(s).
Another embodiment of the present invention uses a double sided endless drive belt that wraps around the three drive pulleys, one driven pulley and may or may not use one or more tensioner/idler pulley(s).
By using two or more motors and a variety of centrifugal supercharger components, a system can be made for a specific applicationxe2x80x94such as a motorcycle, snowmobile, watercraft, up to a semi-tractor trailer truck or large industrial stationary engine. In addition, a standard size could be produced to cover a large segment of the most popular vehicles. Because the horsepower and watts would remain constant, a smaller engine could receive higher boost pressure (psi), while a larger engine would receive more air flow (cfm), but less boost pressure (psi). Known fan laws state that if horsepower (hp) is constant, and pressure (psi) drops, then air flow (cfm) increases, and as boost pressure (psi) increases, then air flow (cfm) is reduced.
Another object of the present invention is to make available, at a reasonable cost, a high performance electric supercharger. To this end, the majority of components are common and already available. With suitable modifications, the backing plates, compressor housings, compressor impellers are standard turbo-supercharger components from: Garrett Allied Signal, Holset, Schwitzer, 1H1-Warner, Mitsubishi, etc. The electrified motors can be high amperage 6+ volt aftermarket motors modified for this application from Delco-Remy, Nippon-Denso, etc. The drive belt and pulley housing can be any composition capable of high rotational speeds and stresses associated with this application. The pulleys can be steel, aluminum, or any composite material. The battery cables can be standard high amp 2/0 welding cable, and the batteries can be automotive type available at any auto parts store. The shaft bearings and tensioner bearings can be class 7 (rated at 30,000 rpm) or class 9 (rated at 60,000 rpm) aerospace ceramic ball bearings, Barden ceramic ball bearings (part no. C202SST5), and Koyo high speed steel ball bearings (part. no. 6205ZZCMP5GK7).